We have written "same day" on this site more than once. It is true, and it leaves out the number underneath it. Our mochi dough runs on a forty-eight hour clock.
The clock starts when the dough is steamed. Glutinous rice flour, milk, butter, and sugar go in as a loose batter and come out elastic, and from that morning the dough has two days on it. We count to end of day. Dough steamed Sunday morning is good through close on Tuesday. Two days, not two twenty-four-hour blocks.
Dough that reaches the end of its second day does not get wrapped the next morning. That is the entire rule. It is short enough to be worth writing down instead of keeping in somebody's head, because a window this tight only works if everybody counts it the same way.
The wrapping is a separate job and it happens every morning. Somebody is at the bench before the doors open, pressing seals by hand, one piece at a time. A batch is three bags of dough and comes out to about ninety-five pieces. So the piece you buy was wrapped a few hours ago. The dough under it was steamed this morning or yesterday morning.
That is what "same day" leaves out. The piece is same day. The dough behind it has a window, and the window is what lets us steam on a Sunday for a Monday that turns out busier than the Sunday was.
We do not push the far end of it. By the second afternoon the dough has firmed enough that it handles differently under the hands, and you can feel that in the finished skin. Thicker by a hair. Steaming more often costs us less than wrapping a piece that comes out wrong.
About ninety-five pieces from three bags is most of the arithmetic of the case. Six mochi flavors come out of that, and then the day does whatever it wants. It is why a flavor that sells out in the afternoon comes back the next morning instead of an hour later, and why the answer at the counter is sometimes just no.
If you are taking pieces home, eat them the day you buy them. By then the dough is already partway through its two days.